Nipah virus (NiV) represents a significant pandemic threat with zoonotic transmission from bats-to-humans with almost annual regional outbreaks characterized by documented human-to-human transmission and high fatality rates. Currently, no vaccine against NiV has been approved. Structure-based design and protein engineering principles were applied to stabilize the fusion (F) protein in its prefusion trimeric conformation (pre-F) to improve expression and increase immunogenicity. We covalently linked the stabilized pre-F through trimerization domains at the C-terminus to three attachment protein (G) monomers, forming a chimeric design. These studies detailed here focus on mRNA delivery of NiV immunogens in mice, assessment of mRNA immunogen-specific design elements and their effects on humoral and cellular immunogenicity. The pre-F/G chimera elicited a strong neutralizing antibody response and a superior NiV-specific Tfh and other effector T cell response compared to G alone across both the mRNA and protein platforms. These findings enabled final candidate selection of pre-F/G Fd for clinical development.

Background Multiple active vaccination approaches have proven ineffective in reducing the substantial morbidity and mortality caused by respiratory syncytial virus (RSV) in infants and older adults (aged >= 65 years). A vaccine conferring a substantial and sustainable boost in neutralising activity is required to protect against severe RSV disease. To that end, we evaluated the safety and immunogenicity of DS-Cav1, a prefusion F subunit vaccine. Methods In this randomised, open-label, phase 1 clinical trial, the stabilised prefusion F vaccine DS-Cav1 was evaluated for dose, safety, tolerability, and immunogenicity in healthy adults aged 18-50 years at a single US site. Participants were assigned to receive escalating doses of either 50 mu g, 150 mu g, or 500 mu g DS-Cav1 at weeks 0 and 12, and were randomly allocated in a 1:1 ratio within each dose group to receive the vaccine with or without aluminium hydroxide (AlOH) adjuvant. After 71 participants had been randomised, the protocol was amended to allow some participants to receive a single vaccination at week 0. The primary objectives evaluated the safety and tolerability at every dose within 28 days following each injection. Neutralising activity and RSV F-binding antibodies were evaluated from week 0 to week 44 as secondary and exploratory objectives. Safety was assessed in all participants who received at least one vaccine dose; secondary and exploratory immunogenicity analysis included all participants with available data at a given visit. The trial is registered with ClinicalTrials.gov, NCT03049488, and is complete and no longer recruiting. Findings Between Feb 21, 2017, and Nov 29, 2018, 244 participants were screened for eligibility and 95 were enrolled to receive DS-Cav1 at the 50 mu g (n=30, of which n=15 with AlOH), 150 mu g (n=35, of which n=15 with AlOH), or 500 mu g (n=30, of which n=15 with AlOH) doses. DS-Cav1 was safe and well tolerated and no serious vaccine-associated adverse events deemed related to the vaccine were identified. DS-Cav1 vaccination elicited robust neutralising activity and binding antibodies by 4 weeks after a single vaccination (p<0middot0001 for F-binding and neutralising antibodies). In analyses of exploratory endpoints at week 44, pre-F-binding IgG and neutralising activity were significantly increased compared with baseline in all groups. At week 44, RSV A neutralising activity was 3middot1 fold above baseline in the 50 mu g group, 3middot8 fold in the 150 mu g group, and 4middot5 fold in the 500 mu g group (p<0middot0001). RSV B neutralising activity was 2middot8 fold above baseline in the 50 mu g group, 3middot4 fold in the 150 mu g group, and 3middot7 fold in the 500 mu g group (p<0middot0001). Pre-F-binding IgG remained significantly 3middot2 fold above baseline in the 50 mu g group, 3middot4 fold in the 150 mu g group, and 4middot0 fold in the 500 mu g group (p<0middot0001). Pre-F-binding serum IgA remained 4middot1 fold above baseline in the 50 mu g group, 4middot3 fold in the 150 mu g group, and 4middot8 fold in the 500 mu g group (p<0middot0001). Although a higher vaccine dose or second immunisation elicited a transient advantage compared with lower doses or a single immunisation, neither significantly impacted long-term neutralisation. There was no long-term effect of dose, number of vaccinations, or adjuvant on neutralising activity. Interpretation In this phase 1 study, DS-Cav1 vaccination was safe and well tolerated. DS-Cav1 vaccination elicited a robust boost in RSV F-specific antibodies and neutralising activity that was sustained above baseline for at least 44 weeks. A single low-dose of pre-F immunisation of antigen-experienced individuals might confer protection that extends throughout an entire RSV season. Funding The National Institutes of Allergy and Infectious Diseases. Copyright (c) 2021 Elsevier Ltd. All rights reserved.

Licensed vaccines or therapeutics are rarely available for pathogens with epidemic or pandemic potential. Developing interventions for specific pathogens and defining generalizable approaches for related pathogens is a global priority and inherent to the UN Sustainable Development Goals.Nipah virus (NiV) poses a significant epidemic threat, and zoonotic transmission from bats-to-humans with high fatality rates occurs almost annually. Human-to-human transmission of NiV has been documented in recent outbreaks leading public health officials and government agencies to declare an urgent need for effective vaccines and therapeutics. Here, we evaluate NiV vaccine antigen design options including the fusion glycoprotein (F) and the major attachment glycoprotein (G). A stabilized prefusion F (pre-F), multimeric G constructs, and chimeric proteins containing both pre-F and G were developed as protein subunit candidate vaccines. The proteins were evaluated for antigenicity and structural integrity using kinetic binding assays, electron microscopy, and other biophysical properties. Immunogenicity of the vaccine antigens was evaluated in mice.The stabilized pre-F trimer and hexameric G immunogens both induced serum neutralizing activity in mice, while the post-F trimer immunogen did not elicit neutralizing activity. The pre-F trimer covalently linked to three G monomers (pre-F/G) induced potent neutralizing antibody activity, elicited responses to the greatest diversity of antigenic sites, and is the lead candidate for clinical development. The specific stabilizing mutations and immunogen designs utilized for NiV were successfully applied to other henipaviruses, supporting the concept of identifying generalizable solutions for prototype pathogens as an approach to pandemic preparedness.

Broadly neutralizing antibodies are showing promise in the treatment and prevention of HIV-1, with several now being evaluated clinically. Some lead clinical candidates, including antibodies CAP256-VRC26.25, N6, PGT121, and VRC07-523, have one or more N-linked glycosylation sequons in their variable domains (Fvs) from somatic hypermutation, and these glycans increase chemical heterogeneity, complicating the manufacture of these antibodies as products. Here we propose a general method to remove Fv glycans and use this method to develop engineered versions of these four antibodies with Fv glycans removed. When germline residues were introduced to remove each glycan, antibody properties between wild type and mutant were not significantly altered for CAP256-VRC26.25 and PGT121; however, germline mutants for N6 and VRC07-523 showed increased polyreactivity, which is known to correlate with unfavorable in vivo pharmacokinetics. To reduce polyreactivity induced by removal of Fv glycan, we mutated aromatic residues and arginines structurally proximal to the removed glycan and identified Fv glycan-removed variants with low polyreactivity for N6 and VRC07-523. Two such variants, N6-N72LCQ-R18LCD and VRC07-523-N72LCQ-R24LCD, showed thermostability, neutralization potency and breadth, and half-life in humanized FcRn mice that were similar to their wild-type Fv-glycosylated counterparts. The removal of Fv glycan and reduction of chemical heterogeneity were confirmed by liquid chromatography-mass spectrometry. With reduced heterogeneity, the Fv-glycan-removed variants developed here may have utility as products for treating or preventing infection by HIV-1.

Technologies that define the atomic-level structure of neutralization-sensitive epitopes on viral surface proteins are transforming vaccinology and guiding new vaccine development approaches. Previously, iterative rounds of protein engineering were performed to preserve the prefusion conformation of the respiratory syncytial virus (RSV) fusion (F) glycoprotein, resulting in a stabilized subunit vaccine candidate (DS-Cav1), which showed promising results in mice and macaques. Here, phase I human immunogenicity data reveal a more than 10-fold boost in neutralizing activity in serum from antibodies targeting prefusion-specific surfaces of RSV F. These findings represent a clinical proof of concept for structure-based vaccine design, suggest that development of a successful RSV vaccine will be feasible, and portend an era of precision vaccinology.

Broadly neutralizing antibodies (bnAb) were identified at the Vaccine Research Center (VRC) at NIH, towards the development of an anti-HIV vaccine. Examples of two such mAbs are CAP256 LS and N6 LS, targeting the V1V2 and CD4-binding sites, respectively, on the gp120 envelope glycoprotein. As part of mAb formulation development, it is critical to identify condition which can maintain the conformational and colloidal stability of the antibodies at 100mg/ml in frozen or liquid phase for two years. The factors which have the maximum impact on stability are formulation pH, ionic strength and stabilizers. High throughput methods to screen these three factors and identify optimal conditions are described here. The initial characterization of the mAbs using techniques including Differential Scanning Calorimetry (DSC), Dynamic Light Scattering (DLS), and Circular Dichroism (CD) indicated that they have very different physico-chemical properties. An assessment of intrinsic stability was conducted using Isothermal Chemical Denaturation (ICD) at a wide pH (4-8) and salt concentration range (0-200 mM). pH had the strongest effect on both CAP256LS and N6LS intrinsic stability. CAP256LS was most stable at a higher pH (>7) while N6LS stability improved above pH 6. Ionic strength had little effect on intrinsic stability for both mAbs. The stabilizing effects of various excipients on CAP256LS was screened using DLS, UV-Visible Spectroscopy, and Size Exclusion Chromatography (SEC). ICD was utilized to more rapidly screen the optimal concentration of these excipients. Balancing the results of the pH and ionic strength screens for both assays, optimal conditions were selected for both mAbs, and the high-throughput screening capacity of the ICD in conjunction with traditional stability-indicating assays helped identify optimal formulation conditions.

Monoclonal antibodies (mAbs) used as therapeutics often require formulation at high concentrations to minimize administration volume. High concentration poses an increased risk of instability, primarily via complicated aggregation pathways. Identification of consistently reliable tools to predict longer term stability based on initial data remains a challenge in the biotechnology industry, especially in the context of protein aggregation. Aggregation is influenced by both colloidal and conformational stability. Colloidal stability can be evaluated by dynamic light scattering (DLS) and used to derive the diffusion coefficient based self-association constant (kD), which is representative of intermolecular attraction. Isothermal chemical denaturation (ICD), differential scanning calorimetry (DSC), and extrinsic and intrinsic fluorescence evaluate conformation and thermodynamic stability. The Gibbs Free Energy (ΔG), an indicator of the propensity for structural transition, is obtained through chemical denaturation. Thermal denaturation monitored via DSC and/or intrinsic and extrinsic fluorescence provides the temperature of onset (Tonset) and the midpoint (Tm) of molecular transitions. In this work, we evaluate the ability of these methods to predict the long-term aggregation for a series of monoclonal antibodies based on their intrinsic molecular properties.

Monoclonal antibodies (mAb) intended for use in prophylactic therapy often require formulation at concentrations of ≥ 100 mg/mL, due to limit in the volume for administration via the subcutaneous injection. This poses challenges for the mAb formulation field in general, but especially for mAbs where protein engineering options are limited due to unique functional characteristics. The work presented will be a case study of a monoclonal antibody (mAb1) developed by the Vaccine Research Center (NIAID/NIH). mAb1 is an exciting candidate for prophylactic HIV therapy based on its capability to neutralize >95% of circulating HIV-1 strains (based on a 208-virus panel). With a range of molecular and structural biology approaches a selection of sequential variants of mAb1 were identified that retained or improved the biological activity of the native strain. mAb1 in the wild-type form has very poor solubility (<5 mg/mL); although solubility was increased in the selected variants, it was insufficient for manufacturing and clinical used. Here we present an exploration of a myriad of formulation options to identify solution conditions that will support the clinical manufacturing of the 10E8 mAb. Specifically, we discuss the critical role that Arginine played in achieving a high concentration formulation.

Highly effective HIV-1-neutralizing antibodies could have utility in the prevention or treatment of HIV-1 infection. To improve the potency of 10E8, an antibody capable of near pan-HIV-1 neutralization, we engineered 10E8-surface mutants and screened for improved neutralization. Variants with the largest functional enhancements involved the addition of hydrophobic or positively charged residues, which were positioned to interact with viral membrane lipids or viral glycan-sialic acids, respectively. In both cases, the site of improvement was spatially separated from the region of antibody mediating molecular contact with the protein component of the antigen, thereby improving peripheral semi-specific interactions while maintaining unmodified dominant contacts responsible for broad recognition. The optimized 10E8 antibody, with mutations to phenylalanine and arginine, retained the extraordinary breadth of 10E8 but with ∼10-fold increased potency. We propose surface-matrix screening as a general method to improve antibodies, with improved semi-specific interactions between antibody and antigen enabling increased potency without compromising breadth.

Different factors affect the long term stability of monoclonal antibodies, among them denaturation or partial denaturation that is often followed by aggregation. Isothermal calorimetry is capable of quantifying the kinetics of denaturation/aggregation of an antibody by measuring the heat that is released or absorbed by the process over a period of days or weeks, at temperatures below its denaturation temperature, T-m. The denaturation/aggregation kinetics of the anti-HIV monoclonal antibody VRC07-52318 was measured by isothermal calorimetry at different concentrations in four different formulation buffers. The measurements were performed at ten degrees below T-m as determined by differential scanning calorimetry. The formation of aggregates was also followed by size exclusion chromatography at 5 degrees C, 25 degrees C and 40 degrees C over a period of 8-36 weeks. It was observed that the rates measured by isothermal calorimetry correlate quantitatively with those measured by size exclusion chromatography. Since isothermal calorimetry experiments are performed over a period of ten days, it can become a valuable tool for a fast prediction of the best formulations.

The zoonotic equine encephalitis viruses (EEVs) can cause debilitating and life-threatening disease, leading to ongoing vaccine development efforts for an effective virus-like particle (VLP) vaccine based on 3 strains of EEV (Eastern, Western, and Venezuelan or EEE, WEE and VEE VLPs, respectively). In this work, transmission electron microscopy and light scattering studies showed enveloped, spherical, and -70 nm sized VLPs. Biophysical studies demonstrated optimal VLP physical stability in the pH range of 7.5-8.5 and at temperatures below -50 degrees C. Interestingly, the individual stability profiles differed notably between the 3 VLPs. Numerous pharmaceutical excipients were screened for their VLP stabilizing effects against thermal stress. Sucrose, sorbitol, sodium chloride, and pluronic F-68 were identified as promising stabilizers and the concentrations and combinations of these additives were optimized. Candidate monovalent VLP bulk formulations were incubated at temperatures ranging from -80 degrees C to 40 degrees C to establish freeze-thaw, long-term (2 degrees C-8 degrees C) and accelerated stability trends. Good VLP stability profiles were observed at each storage temperature, except for a distinct instability observed at -20 degrees C. The interaction of monovalent and trivalent VLP formulations with aluminum adjuvants was examined, both in terms of antigen adsorption and desorption over time. The implications of these findings on future vaccine formulation development of EEV VLPs are discussed. (c) 2018 American Pharmacists Association (R). Published by Elsevier Inc. All rights reserved.

Structure-based vaccine design has been used to develop immunogens that display conserved neutralization sites on pathogens such as HIV-1, respiratory syncytial virus (RSV), and influenza. Improving the immunogenicity of these designed immunogens with adjuvants will require formulations that do not alter protein antigenicity. Here, we show that nanoparticle-forming thermoresponsive polymers (TRP) allow for co-delivery of RSV fusion (F) protein trimers with Toll-like receptor 7 and 8 agonists (TLR-7/8a) to enhance protective immunity. Although primary amine conjugation of TLR-7/8a to F trimers severely disrupted the recognition of critical neutralizing epitopes, F trimers site-selectively coupled to TRP nanoparticles retained appropriate antigenicity and elicited high titers of prefusion-specific, TH1 isotype anti-RSV F antibodies following vaccination. Moreover, coupling F trimers to TRP delivering TLR-7/8a resulted in ∼3-fold higher binding and neutralizing antibody titers than soluble F trimers admixed with TLR-7/8a and conferred protection from intranasal RSV challenge. Overall, these data show that TRP nanoparticles may provide a broadly applicable platform for eliciting neutralizing antibodies to structure-dependent epitopes on RSV, influenza, HIV-1, or other pathogens.

Adequate protein solubility is an important prerequisite for development, manufacture, and administration of biotherapeutic drug candidates, especially for high-concentration protein formulations. A previously established method for determining the relative apparent solubility (thermodynamic activity) of proteins using polyethylene glycol (PEG) precipitation is adapted for screening and comparing monoclonal antibody (mAb) candidates where only limited quantities (≤1 mg) are available. This micro-PEG assay is used to evaluate various broadly neutralizing mAb candidates to HIV-1 viral spike (gp120 and gp41 glycoproteins). Using ∼1 mg of VRC01-WT mAb per assay, the precision of the micro-PEG assay was established. A series of 7 different broadly neutralizing mAbs to the HIV-1 viral spike proteins were compared by curve shape (%PEG vs. protein concentration), %PEGmidpoint determinations, and extrapolated apparent solubility values. Numerous formulation conditions were then evaluated for their relative effects on the VRC01-WT mAb. The PEGmidpt and apparent solubility values of VRC01-WT mAb decreased as the solution pH increased and increased as NaCl and arginine were added. A final optimization of the micro-PEG assay established that amounts as low as 0.1-0.2 mg can be used. Thus, the micro-PEG assay has significant potential as a relative solubility screening tool during candidate selection and early formulation development.

Chikungunya virus (CHIKV) is an alphavirus that infects millions of people every year, especially in the developing world. The selective expression of recombinant CHIKV capsid and envelope proteins results in the formation of self-assembled virus-like particles (VLPs) that have been shown to protect nonhuman primates against infection from multiple strains of CHIKV. This study describes the characterization, excipient screening, and optimization of CHIKV VLP solution conditions toward the development of a stable parenteral formulation. The CHIKV VLPs were found to be poorly soluble at pH 6 and below. Circular dichroism, intrinsic fluorescence, and static and dynamic light scattering measurements were therefore performed at neutral pH, and results consistent with the formation of molten globule structures were observed at elevated temperatures. A library of generally recognized as safe excipients was screened for their ability to physically stabilize CHIKV VLPs using a high-throughput turbidity-based assay. Sugars, sugar alcohols, and polyanions were identified as potential stabilizers and the concentrations and combinations of select excipients were optimized. The effects of polyanions were further studied, and while all polyanions tested stabilized CHIKV VLPs against aggregation, the effects of polyanions on conformational stability varied.

Freeze-thawing is a potentially damaging stress to which therapeutic proteins can be exposed deliberately during storage of bulk drug substance, and accidentally because of mishandling of commercial product during shipping and/or storage. The primary route of degradation induced by freeze-thawing is protein aggregation. We studied the effects of freeze-thawing on aggregation of an IgG2 monoclonal antibody, examining solution conditions (pH, and the presence or absence of 150 mM KCl), protein concentration, cooling and warming rates, and container type and material. In addition, we determined the effect of pH and KCl on protein tertiary structure and thermal stability with second derivative UV spectroscopy. In general, aggregation of the antibody during freeze-thawing increased with decreasing pH, which correlated well with Tm values. Aggregation was most prevalent at pH 3 and 4, with potential mechanisms involving both the formation of aggregation-prone conformational states as well as adsorption to and denaturation at various interfaces. Although all the parameters examined demonstrated some effect on the formation of soluble aggregates, the effect of container material was especially pronounced. Samples stressed in plastic or glass containers contained low amounts of aggregate. Storage in Teflon or commercial freezing containers, however, led to significantly higher levels of aggregate formation.

We describe an alternate approach for studying protein structure using the detection of ultraviolet (UV) absorbance peak shifts of aromatic amino acid side chains induced by the presence of salts. The method is based on the hypothesis that salt cations (Li+, Na+, and Cs+) of varying sizes can differentially diffuse through protein matrices and interact with benzyl, phenyl, and indole groups through cation-pi interactions. We have investigated the potential of this method to probe protein dynamics by measuring high resolution second-derivative UV spectra as a function of salt concentration for eight proteins of varying physical and chemical properties and the N-acetylated C-ethyl esterified amino acids to represent totally exposed side chains. We show that small shifts in the wavelength maxima for Phe, Tyr, and Trp in the presence of high salt concentrations can be reliably measured and that the magnitude and direction of the peak shifts are influenced by several factors, including protein size, charge, and the local environment and solvent accessibility of the aromatic groups. Evaluating the empirical UV spectral data in light of known protein structural information shows that probing cation-pi interactions in proteins reveals unique information about the influence of structure on aromatic side chain spectroscopic behavior.

We examine biochemical characteristics of the herpes simplex virus.(HSV) tegument protein VP22 by gel filtration, glycerol sedimentation, and chemical cross-linking experiments and use time course radiolabeling and immunoprecipitation assays to analyze its synthesis and interaction with other infected-cell proteins. VP22 was expressed as a delayed early protein with optimal synthesis requiring DNA replication. In immunoprecipitation assays, VP22 was found in association with several additional proteins including VP16 and a kinase activity likely to be that of UL13. Furthermore, in sizing chromatography experiments, VP22 was present in several higher-order complexes in infected cells. From gel filtration analysis the major form of VP22 migrated with a molecular mass of approximately 160 kDa, consistent with its presence as a tetramer, or a dimer complexed with other proteins, with a fraction of the protein migrating at larger molecular mass. In vitrosynthesized VP22 sedimented in a size range consistent with a mixture of tetramers and dimers. Short N- or C-terminal deletions resulted in migration almost exclusively as dimers, indicating that VP22, in the absence of additional virus-encoded proteins, could form higher-order assemblies, most likely tetramers, but that both N-and C-terminal determinants were required for stabilizing such assemblies. Consistent with this we found that isolated proteins encompassing either the N-terminal or C-terminal region of VP22 sedimented as dimers, and that the purified C-terminal domain could be cross-linked into dimeric structures. These results are discussed with regard to possible virus and host interactions involved in VP22 recruitment into virus particles.